It takes time, its a lot of work and practice, but its a good way to keep fit and once you have learned and practiced so that the movements are instinctive you can protect yourself. My 13 year old daughter takes a class with adults because of her size and her natural inclination to fight. Kid never gives up in a match or shows fear even when she is injured or her opponent is much larger than her. When we signed her up for her classes I was warned she probably would injure herself on a fairly regular basis. She's broken fingers and toes and she hurt her ankle and knee a few times, but she still goes back because she loves it. So, I guess small personal injuries are a potential downside to training but if it saves your life some day that's a small price to pay.